Disclosed are a fused pyrimidine compound, an intermediate, a preparation method therefor, and a composition and an application thereof. The present invention provides a fused pyrimidine compound shown in formula I, pharmaceutically acceptable salt, hydrate, solvate, and an optical isomer or prodrug of the compound. The present invention further provides applictions of the fused pyrimidine compound shown in formula I, the pharmaceutically acceptable salt, the hydrate, solvate, and the optical isomer or the prodrug of the compound in the preparing drugs for curing and/or preventing a kinase-related disease. The fused pyrimidine compound I of the present invention is an efficient PI3 kinase depressor, and can be used to prepare drugs for preventing and/or curing cell-proliferation diseases such as cancer, infection, inflammation, and an autoimmune disease.
